This proposal aims to acquire a FEI Apreo VS scanning electron microscope (SEM) with VolumeScope capabilities for both conventional SEM and state-of-the-art serial block-face (SBF)-SEM. The instrument uses a physical ultramicrotome to sequentially remove a layer and then image the newly exposed block-face by SEM. The iterative process is fully automated and can generate 3D z-stacks containing hundreds of images. SBF- SEM was previously limited by the minimal sectioning thickness, however using FEI?s multi-energy deconvolution technology, 10 nm isotropic voxels can be acquired to generate high resolution 3D data sets of large volumetric samples. This makes SBF-SEM especially well-suited to the multi-scale biological problems of our 9 major users, all of which have small nanoscopic features that must be examined in the context of large 3D structures. A major focus is the measurement of nanoscopically thin fibers that are long, but tightly packed. Our major users and their projects include Dr. Elliott and Dr. Killian, who will examine collagen fibrils in tendons and the complex fibrous network at tissue interfaces; Dr. Jia will similarly resolve 3D nanostructures in vocal-fold tissue layers. Dr. Duncan and Dr. Lachke will measure changes in membrane protrusions in long lens fiber cells during eye development. Other major users include Dr. Griffin, using SBF-SEM to examine mouse brain synapses, Dr. Wei will image Xenopus olfactory development, Dr. Muniswamy will evaluate changes in cardiac mitochondrial morphology, and Dr. Gleghorn will quantify multi-scale vascular networks in developing lung tissue. Half of the major users and all of the minor users are already using the 15-year old SEM that we seek to replace. The Apreo VS will be an exceptional system to meet both the needs of our current SEM users and new SBF-SEM users because it can rapidly switch between conventional SEM and SBF-SEM. The FEI Apreo VS will be placed in and managed by the Delaware Biotechnology Institute?s (DBI) Bio-Imaging Center at the University of Delaware (UD), which is a hub for imaging and research activity at UD. The institutional commitment by DBI and UD is long established and very strong. Commitments include space, personnel, service contract, and administrative support. A 5-year financial plan has been provided to ensure the long-term sustainability. The Bio-Imaging Center has a strong track record for providing excellent and sustained user support and resource management. The SBF-SEM requires a variety of technical expertise: four full-time staff members will provide expertise in sample preparation (Shannon Modla/Jean Ross), SEM operation (Deborah Powell/Jean Ross), and 3D image visualization and analysis (Jeff Caplan). The FEI Apreo VS will be the only SBF-SEM in the State of Delaware. Our goal is to make it accessible as a regional resource. To show that commitment, we have included Dr. Muniswamy (Major User) and Nancy Pleshko (Advisory Committee) from Temple University. Bringing SBF-SEM to the region will greatly enhance the current research projects (presented here) and will also enable new users and research projects across Delaware and beyond.